In a power substation there can be a dozen or more primary devices, such as circuit breakers, power transformers and distribution transformers. The circuit breakers may vary in type, age and brand and may even include different parts. Hundreds of thousands of circuit breakers are in operation over the world.
Power substation equipment is to be very reliable and show a high availability. It has to be ensured that circuit breakers operate at all times in case of the desire for interruption or reconnection of power connections. High reliability and availability may be important as well for distribution transformers and power transformers in substations. Therefore, the quality of the primary devices can be checked regularly by a service technician to ensure this.
Power substations can be located in remote areas. The supervision of these remote power substations can be time and cost consuming. Between successive checks by a service technician, a probability of a component malfunction may increase, due to unavoidable degradation of the component or due to a particular operation, which would be detected only at the next service interval. Furthermore, in the case of a problem, a service technician may have to arrive at the power substation to determine the cause of the problem and to repair it. The required spare parts need to be available to him. Missing parts may be a problem leading to a delay of the repair.
Simple monitoring devices are known to monitor, based on operational diagnostic data, power substation equipment during operation. The monitoring devices may act as non-intelligent data loggers. Such monitoring devices can have only a static setup for thresholds and sampling of data. The data may then be communicated to a high level system and processed centrally.
Furthermore, more sophisticated but still locally operating diagnostic devices may be based on fixed rules that are entered during commissioning and reflect the specific type of installation. This can be done by setting specific limits or parameters. A deviation of operational diagnostic data from the given limits according to the fixed rules may be signalled as an alarm.